package com.eistert.java.datastructure._03_Queue;


/**
 * @Author: ai
 * @create: 2023-04-04 16:26
 */
public class _02_LoopQueue<E> implements Queue<E> {
    private E[] data;

    private int front, tail;

    /**
     * todo  LoopQueue中不声明size
     * 有兴趣的同学，在完成这一章后，可以思考一下：
     * LoopQueue中不声明size，如何完成所有的逻辑？
     * 这个问题可能会比大家想象的要难一点点：）
     */
    private int size;

    public _02_LoopQueue(int capacity) {
        data = (E[]) new Object[capacity + 1];
        front = 0;
        tail = 0;
        size = 0;
    }

    public _02_LoopQueue() {
        this(10);
    }

    public int getCapacity() {
        return data.length - 1;
    }

    @Override
    public int getSize() {
        return size;
    }

    /**
     * if front == tail,then loopqueue is empty
     * <p>
     * if tail+1 == front loopqueue size if full.
     *
     * @return
     */
    @Override
    public boolean isEmpty() {
        return front == tail;
    }

    @Override
    public void enqueue(E e) {
        /**
         * judge loopqueue is full
         */
        if ((tail + 1) % data.length == front) {
            resize(getCapacity() * 2);
        }

        data[tail] = e;
        tail = (tail + 1) % data.length;
        size++;
    }

    @Override
    public E dequeue() {
        if (isEmpty()) {
            throw new IllegalArgumentException("cannot dequeue from an empty queue.");
        }

        E ret = data[front];
        data[front] = null;
        front = (front + 1) % data.length;
        size--;

        /**
         * 缩容到原来容量的1/2,且缩容不能为0
         */
        if (size == getCapacity() / 4 && getCapacity() / 2 != 0) {
            resize(getCapacity() / 2);
        }

        return ret;
    }

    /**
     * @return
     */
    @Override
    public E getFront() {
        if (isEmpty()) {
            throw new IllegalArgumentException("Queue is empty.");
        }

        return data[front];
    }

    /**
     * resize the loopqueue
     *
     * @param newCapacity
     */
    private void resize(int newCapacity) {
        E[] newData = (E[]) new Object[newCapacity + 1];

        for (int i = 0; i < size; i++) {
            newData[i] = data[(i + front) % data.length];
        }

        data = newData;
        front = 0;
        tail = size;
    }

    @Override
    public String toString() {

        StringBuilder res = new StringBuilder();
        res.append(String.format("Queue: size = %d , capacity = %d\n", size, getCapacity()));
        res.append("front [");
        for (int i = front; i != tail; i = (i + 1) % data.length) {
            res.append(data[i]);
            if ((i + 1) % data.length != tail)
                res.append(", ");
        }
        res.append("] tail");
        return res.toString();
    }

    public static void main(String[] args) {
        _02_LoopQueue<Integer> queue = new _02_LoopQueue<>();
        for (int i = 0; i < 10; i++) {
            queue.enqueue(i);
            System.out.println(queue);

            if (i % 3 == 2) {
                queue.dequeue();
                System.out.println(queue);
            }
        }
    }
}
